Chip forming insert, especially for turning and slotting

ABSTRACT

The invention relates to a cutting insert for machine tools wherein the insert adjacent its cutting edge has a chip forming device. The insert has a cutting edge and a planar surface adjoining the cutting edge. A recess is located downstream of the cutting edge and adjoining the planar surface. Various surfaces defining the recess are designed to engage a formed chip and bend it laterally. Obliquely upwardly directed abutment surfaces adjoining the planar surface are adapted to engage the edge flanks of the chip and bend the chip upwardly for breaking the chip into pieces.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

This invention relates to cutting bits or inserts for cutting workespecially turning wherein the insert is detachably held in a toolholder of a lathe or similar machining apparatus.

2. Description of the Prior Art

Within the technical field is known a cutting bit insert which adjacentto the cutting edge presents a recess, down into which the middleportion of the chip is pressed during the machining operation. The sideportions of the insert are kept in a somewhat higher plane in order togive the chip a lateral bending so that it will have less width than ithas just upon leaving the cutting edge and thereby becomes narrower thanthe groove cut. The laterally bent chip can then roll itself and form acoil, which is narrower than the turned groove and does not causesdamage to the machined surfaces or the like.

Within this field, it is also known to arrange, remote from the cuttingedge of any tool, a chip breaker, that is a protruding portion whichwill be engaged by the cut chip in order to be guided away abruptly.This results in a breaking of the chip preventing it from formingcontinuous coils, spirals or spools which in turn might cause tooldamages or damage to the work piece and machined surfaces. However, inthis arrangement the chip is subjected to deformation during thebreaking off process which increases its lateral width and tends tocause congestion of chips and poor surface finish on the side surfacesof the groove.

One essential aspect of this invention is to provide a new cuttinginsert that causes lateral bending of the chip and also causes it tobreak thereby producing short chips having less width than the groovecut. Such chips being easily removed from the groove without tendency toadhere to the sides of the groove, the tool or the like.

SUMMARY OF THE INVENTION

The cutting insert according to the present invention has projectionsdownstream of the cutting edge, in the direction of movement of thechip, to guide the chip away from the planar surface adjacent thecutting edge and act as chip breaker. The projections being arrangedlaterally remote from each other. Between the projections adjacent thecutting edge, is a concave middle recess having obliquely arranged andconcave surfaces along its sides.

A chip cut from a work piece slides inwardly over the middle recessarranged adjacent the cutting edge and is thereupon subjected to aninitial lateral bending as the portion of the chip still attached to thework piece presses the free portion of the chip against the surfaceadjacent the cutting edge. Simultaneously, the edge flanks of the chipare guided by the side portions of the planar surface on either side ofthe recess toward the projections. The force the chip still attached tothe work piece by an intermediate portion and pushed forwardly therebyto bend upwardly so the chip portion between the projections eventuallyleaves the bottom of the middle recess and floats freely between theprojections. With the chip then heavily deformed both in its length andlateral directions, the chip will break beyond the top portions of theprojections and form laterally bent or arched and lengthwise curvedshort chip pieces having smaller width than the groove cut by thecutting edge.

BRIEF DESCRIPTION OF THE DRAWING

The above as well as other features and advantages of the invention willbe apparent through consideration of the detailed description inconnection with the several drawings in which:

FIG. 1 is a side elevational view showing a cutting insert according tothe invention,

FIG. 2 is a front elevational view of the same insert,

FIG. 3 is a top plan view of the cutting insert, and

FIG. 4 is a cross-sectional view taken along the line C--C of FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

The cutting insert 1, the main features of which essentially correspondto those of a known insert, has a V-shaped bottom ridge 2 and an upperabutment surface 3. The V-shaped bottom ridge 2 is intended to cooperatewith a V-groove (not shown) of an insert holder (not shown) while theupper abutment surface 3 is intended to be engaged by an abutmentportion (not shown) of the holder in order to hold it in position in theinsert holder by grasping the shank portion 4 of the insert 1.

The insert 1 has a front edge 5 and a planar surface 6. The surface 6has a middle portion 7 and side portions 10. The middle portion 7 isnarrower in the direction of movement of the chips than the wider sideportions 10. The middle portion 7 passes into recess 8 having a concavebottom and defined by convex outwardly inclined side walls 9.

The recess 8 permits the central portion of the cut chip (not shown) tobe displaced downwardly below the level of the edge flanks of the chipwhich are guided by the side portions 10 of the surface 6 therebybending or arching the chip in a lateral direction. The side walls 9have end edges 11 adjoining the side portions 10 of the surface 6 toform chip breaking abutments. The edge flanks of the chip are guidedabruptly upward by these end edges 11.

Preferably, the angle A (FIG. 1) between the surface 6 and the end edges11 serving as the chip breaker is in the range 45° to 65° and ispreferably about 55°. Further, the angle B (FIG. 2) between same surface6 and the surfaces of the side walls 9 defining the recess 8 is in therange 20° to 40° and is preferably 30° about 30°.

The lateral bending of the chip through cooperation of the surface 6 andthe recess 8 results in a reduction of the width of the chip so itbecomes considerably narrower than the groove cut by the insert 1. Thechip thereby avoids contact with the sides of the groove which wouldotherwise cause the chip to be pulled along the work piece or toolscausing damage thereto. The guiding or bending upwardly of the laterallybent chip through contact with the end edges 11 results in the chipbreaking off in rather short pieces because of the high material stressbrought about by the deformations. The small pieces fall away from theworking area without causing damage. A cutting fluid can be added duringthe cutting process to facilitate the removal of the broken off piecesof chip.

The invention is not limited to the embodiment shown above but can bevaried within the framework of the following patent claims.

I claim:
 1. A cutting insert for mounting in an insert holder of a latheor similar machining apparatus for performing a cutting operation on awork piece, comprising:(a) a cutting edge; (b) a surface adjoining saidcutting edge and extending in a plane, said surface having a middleportion and two side portions adjacent said middle portion; (c) bottomand side recess surfaces defining a recess adjoining said middle portionof said surface adjoining said cutting edge downstream in a direction ofmovement of a chip cut from the work piece, said side surfaces of saidrecess being obliquely arranged at an angle in a range of 20° to 40°relative to the plane of said surface adjoining said cutting edge, saidbottom and side surfaces of said recess positioned to engage andlaterally bend a central portion of the chip as the chip is fedrearwardly from said cutting edge while edge flanks of the chip arecarried by said side portions of said surface adjoining said cuttingedge; and (d) an abutment end surface adjoining each of said sideportions of said surface adjoining said cutting edge and positioneddownstream in a direction of movement of the chip cut from the workpiece, said abutment end surfaces being arranged at angle in a range of45° to 65° relative to the plane of said surface adjoining said cuttingedge, whereby said abutment end surfaces engage the edge flanks of thechip for continually bending the edge flanks away from the plane of saidsurface adjoining said cutting edge and causing an abrupt bending of thechip which results in a breaking of the chip.
 2. The cutting insertaccording to claim 1, wherein the angle between the plane of saidsurface adjoining said cutting edge and said abutment end surfaces is55° and the angle between the plane of said surface adjoining saidcutting edge and said recess side surfaces is 30°.